The nature of light emitted by lasers, with its characteristic coherence and narrow beam divergence, is such that exposure of the eye to relatively small laser energies can result in damage to the retina.
At the present time there is no acceptable instrument for determining compliance with the legally established performance safety standards for lasers and laser products, and there is need for an improved instrument which can measure laser energy in the visible band and which can determine the time at which the optical energy will exceed the accessible emission limit for a Class I laser, and more specifically, which is capable of measurement accuracy of the order of .+-.3 percent for CW or pulsed signals where the peak power is between 10 .mu.W and 100 mW and the pulses are greater than 18 .mu.sec. in width, and which is portable for field use.
A body of patent literature exists which patents disclose devices for converting light signals into electrical signals, but these do not serve the intended purpose. Such U.S. Patents, and others noted during a preliminary search are: Rex U.S. Pat. No. 3,687,558; Yata et al U.S. Pat. No. 3,836,262; Egli et al U.S. Pat. No. 3,843,265; List U.S. Pat. No. 3,846,028; Mohler U.S. Pat. No. 3,966,325; Frank et al U.S. Pat. No. 4,008,966; Jenkins et al U.S. Pat. No. 4,035,088 and Maeda U.S. Pat. No. 4,201,472.